Reinforcement fiber bundle and production method of such reinforcement fiber bundle

ABSTRACT

A reinforcement fiber bundle and method for joining reinforcement fibers to reinforcement fiber bundles for reinforcement wherein a curable material is provided in which reinforcement fibers are bundled in a substantially parallel position and at least at the ends are joined, in which at least the ends of the reinforcement fibers are joined by means of an adhering substance that is substantially inert in relation to the non-cured curable material and that, when the reinforcement fiber bundles are mixed with at least the curable material, loses its cohesion.

[0001] The present invention relates, in a first aspect, to areinforcement fiber bundle, comprising a number of substantiallyparallel reinforcement fibers for reinforcing a curable material, whichreinforcement fibers are joined at least at the ends thereof by means ofan adhering substance, which loses its cohesion under the influence ofmechanical forces during mixing of the reinforcement fibers bundles withat least the curable material.

[0002] Such reinforcement fiber bundle is known from WO-A-00/49211. Inthis document, reinforcement fibers for castable compositions such asconcrete, are bundled and joined at the ends by means of a layer ofbinding material applied on the ends. The binding material is eitherdissolved by the castable composition or dispersible in the aggregatestherein. As a result, the bundle disintegrates and the fibres areliberated.

[0003] Such reinforcement fiber bundle has the disadvantage that thebinding material that is dissolved or dispersed is absorbed by thematerial that has to be cast or cured. As the aforementionedreinforcement fiber bundle is meant to increase the ratio ofreinforcement fibers to the curable material, a considerable quantity ofbinding material will be dissolved or dispersed in the curable material.This entails the risk that the properties of the curable material areadversely influenced. Therefore, there is need for a reinforcement fiberbundle of which a large part of the reinforcement fibers can beintegrated in the curable material without adding substances that becomedissolved or dispersed in or react with the curable material.

[0004] The invention intends to solve the aforementioned problem andthereto is characterized in that the adhering substance substantiallycomprises a material which is substantially inert with respect to thenon-cured curable material.

[0005] By “inert with respect to the non-cured curable material” thepresent application understands that the adhering substancesubstantially does not react with the conventional curable materialsthat still have to be cured or with mixtures of such materials,regardless of the fact whether conventional additives are added or not.More particularly, the adhering substance is substantially non-solublein water and/or organic solvents.

[0006] When the reinforcement fiber bundles are mixed with the curablematerial, the adhering substance may lose its cohesion in many ways. Atemperature treatment e.g. can cause the adhering substance to fallapart into smaller pieces. Moreover, the aforementioned mechanicalforces appear e.g. by friction of the reinforcement fiber bundles withother reinforcement fiber bundles, the walls of the recipient, themixing means, gravel that may be present in the curable material, etc.Because of these mechanical forces during the mixing process, theadhering substance will be divided into ever-smaller pieces till thereinforcement fibers are no longer joined and can be spread separatelyin curable material.

[0007] Preferably, the adhering substance is a curing substance. Suchsubstance may be applied in a viscous condition on the reinforcementfibers, and be subsequently cured by drying, heating, etc. In principle,however, it is also possible to use a non-curing substance as adheringsubstance, provided the appropriate and/or sufficiently large mechanicalforces are applied. It is e.g. possible to choose a tenacious adheringsubstance, in combination with which e.g. moving knives guarantee thatthe cohesion of the adhering substance is lost and that thereinforcement fibers are separated.

[0008] Preferably, the adhering substance substantially comprises thecurable material. In that way, it is extremely efficiently ensured thatthe properties of the curable material will be very little or notinfluenced by the adhering substance. The finally cured curable materialwill be a homogeneous material, apart from the reinforcement fibers,which have been spread in the meantime. It is possible that one or moreappropriate additive substances are added to the curable material, orthat the mixing ratios of the components of the concrete mixture differslightly for the adhering substance and the curable material. It ishowever possible to choose different materials for the adheringsubstance and the curable material.

[0009] Although preferably the adhering substance substantiallycomprises the curable material, it may comprise widely used additives.E.g. a small amount of a material that promotes abrassion, or otherwiseinfluences mechanical properties of the adhering substance, may beadded.

[0010] Advantageously, the adhering substance substantially comprisesmortar, concrete, gypsum, cement or a mixture thereof. These adheringsubstances are particularly suitable for use in concrete orconcrete-like materials. These curable materials are very widely used ase.g. building materials. They are very strong, but also relativelybrittle. To improve their strength, and especially their fracturingbehavior, these materials are often reinforced by means of reinforcementfibers. The use of adhering substances according to the inventionensures that the basic matrix of the final concrete or concrete-likematerial is substantially unaltered. The proposed adhering substancesvery much resemble concrete-like materials. It is to be noted, however,that, if gypsum is used, the gypsum should be used in a lowconcentration, such that e.g. the curing time and other features of theconcrete are not influenced negatively.

[0011] In a particularly advantageous embodiment of the invention theadhering substance comprises secondary reinforcement fibers. By addingsuch secondary reinforcement fibers to the adhering substance, thelatter has a larger strength and malleability. This allows toefficiently use an adhering substance that per se does not havesufficient mechanical strength as adhering substance. As the mechanicalstrength of the adhering substance has been increased with secondaryreinforcement fibers, the bulk storage, and the transport and pour-outbehavior of the reinforcement fiber bundles can be improved.

[0012] In principle, the secondary reinforcement fibers can be made ofany material, though they preferably comprise glass fibers orpolypropene fibers with a maximum diameter of 100 μm. Such fibers areefficient and it is not difficult to manufacture the desired diameter.

[0013] Advantageously, the length-diameter ratio of the reinforcementfiber bundles is at least 0.2 and maximally 5. Such length-diameterproperties ensure good manageability and pour-out properties out ofstorage silos of reinforcement fiber bundles. If the length-diameterratio exceeds the aforementioned range, the risk of bridging in storagesilos increases. Nevertheless, reinforcement fiber bundles of which thelength-diameter ratio exceeds the aforementioned range, can be usedunder particular conditions. More advantageously, the length-diameterratio of the reinforcement fiber bundles is at least 0.5 and maximally1.5. In the event of such length-diameter ratio, the reinforcement fiberbundles substantially resemble a cylinder or block, resulting in verygood pour-out properties and excellent manageability. Preferably, thelength-diameter ratio of the reinforcement fiber bundles substantiallyamounts to 1.

[0014] The reinforcement fiber bundle can have any shape, though it ispreferably substantially cylindrical. In the case of a cylindricalshape, the reinforcement fiber bundles have no or practically no cornersand/or tips, ensuring even better manageability and pour-out properties.Nevertheless, other shapes are also possible, such as cubes or blocks.In the ideal case, fibers of different lengths are used, with theshortest fibers at the outer contour of the reinforcement fiber bundleand the longest fibers in the middle, thus creating a practicallyspherical reinforcement fiber bundle.

[0015] In principle, the reinforcement fibers that are used can have anydesired length-diameter ratio. Preferably, the length-diameter ratio ofthe reinforcement fibers is at least 40.

[0016] In an advantageous embodiment of the reinforcement fiber bundleaccording to the invention, the reinforcement fibers are made of steelwith a tensile strength between 500 and 3000 N/mm². It is also possibleto choose steel with another tensile strength, but this offers littleadvantages when reinforcing the curable material. But, it may also beefficient to choose other materials for the reinforcement fibers, suchas e.g. carbon fibers, polypropene or other plastics, glass, etc.

[0017] Preferably, the ends of the reinforcement fibers are hook-shaped.In this application, the term “hook-shaped ends” not only refers tofibers being bent at least once at their ends. It is also refers tofibers having ends which are deformed, such that in at least onedirection the diameter of the projection of the deformed end onto aplane perpendicular to a main axis of the reinforcement fiber is largerthan the diameter of that section of the fiber between the ends. Forexample, the ends may be flattened, bent or tortuous, or may have theshape of a nail, and so on. This will be elucidated in the drawings.This improves the adherence of the reinforcement fibers in the curablematerial after curing. In the case of straight reinforcement fibers, itis more likely that these fibers will be pulled out of the curedmaterial when a fracture arises, as a result of which the strength ofthe material is lost. But, there are also other ways to improve theadherence of the reinforcement fibers in the cured curable material,e.g. by flattening the fibers or giving them a corrugated or hook-shapedaspect.

[0018] Preferably, the reinforcement fiber bundle according to theinvention comprises end faces, which are substantially evenly covered bythe adhering substance. So, the end faces of the reinforcement fiberbundles are substantially smooth. This offers the advantage of decreaseddewing between the reinforcement fiber bundles. Ordinarily the ends ofthe reinforcement fibers can be entangled in the ends of thereinforcement fibers of other reinforcement fiber bundles, or also (inthe middle) between the reinforcement fibers of other reinforcementfiber bundles. By evenly covering the ends of the reinforcement fiberswith the adhering substance this is avoided in an efficient way.

[0019] It is also possible that the adhering substance is applied toother or additional parts of the reinforcement fiber bundle. The entirereinforcement fiber bundle can e.g. be surrounded by or even saturatedwith the adhering substance. It is also possible to put a ring ofadhering substance between the ends of the reinforcement fiber bundle.This ensures an even larger mechanical strength and an even smallerinteraction between the reinforcement fiber bundles, though thetreatment time will increase.

[0020] In a preferential embodiment of the reinforcement fiber bundleaccording to the invention, substantially only the hook-shaped ends ofthe reinforcement fibers are comprised in the adhering substance. Inthat way it is still ensured that the hook-shaped ends do not contributeto dewing of the reinforcement fiber bundles, whereas only a very smallquantity of adhering substance is used. Generally it is important to useas little a quantity of adhering substance as possible since it mayadversely affect the curable material. This quantity may be furtherminimized by good alignment of the reinforcement fibers in the bundle.Thus the fiber ends will all be present in as small disk as possible.

[0021] The invention also relates to a method for joining reinforcementfibers into reinforcement fiber bundles for reinforcing a curablematerial, in which reinforcement fibers are bundled in a substantiallyparallel position and are joined at least at the ends, in which thereinforcement fibers are joined by applying to at least the ends of thereinforcement fiber bundle an adhering substance which is substantiallyinert in relation to the non-cured curable material and which, under theinfluence of the mechanical forces during the mixing of thereinforcement fiber bundles with at least the curable material, losesits cohesion.

[0022] Such a method provides in a simple way reinforcement fiberbundles according to the invention with very good manageability andpour-out properties without the adhering substance having a negativeinfluence on the properties of the curable material. Nevertheless, it isalso possible to apply the fibers in a quantity of adhering substance,manually or by means of a “fiber gun” that “shoots” or pricks the fibersin the adhering substance, etc.

[0023] In a preferential embodiment, a curing adhering substance isapplied and subsequently cured. This can be obtained by exposing thereinforcement fiber bundles to which the adhering substance is appliedto a curing treatment, e.g. air-drying, an increased temperature or apolymerization reaction.

[0024] In another preferred method the substantially parallel bundlingof the reinforcement fibers takes place under tension. The advantage isthat the distribution of the reinforcement fibers in the curablematerial is much better when the adhering substance comes off.

[0025] The invention also relates to a reinforcement fiber bundle,comprising a number of substantially parallel reinforcement fibers forreinforcing a curable material, which reinforcement fibers are joined atleast at the ends thereof by means of an adhering substance which losesits cohesion during the mixing of the reinforcement fiber bundles withat least the curable material, wherein the adhering substance comprisesreinforcement fibers.

[0026] The use of secondary reinforcement fibers in the adheringsubstance is not limited to adhering substances that are inert withrespect to the curable material. The advantage of adding secondaryreinforcement fibers, viz. the larger strength and malleability of theadhering substance, as described above, is obtained also in e.g.water-soluble adhering substances. E.g. the adhering substance maycomprise polyvinylacetate, either as a main constituent, or as anadditive to for example a mortar-like adhering substance. In thesecases, the adhering substance becomes much more flexible, and eithercompletely, or at least more water-soluble. Other water-solubleconstituents are possible.

[0027] On the other hand, the mentioned limitations and advantages ofpreferred embodiments of the reinforcement fiber bundle according to thefirst aspect of the invention also hold for the reinforcement fiberbundle according to claim 18.

[0028] A first embodiment is characterized in that the secondaryreinforcement fibers comprise glass fibers and/or polypropene fiberswith a diameter of maximally 100 micrometer.

[0029] In a second embodiment at least the ends of the reinforcementfibers are substantially evenly covered with the adhering substance.

[0030] Expediently, the ends of the reinforcement fibers arehook-shaped.

[0031] In a third embodiment, the thickness of the applied adheringsubstance substantially corresponds to the length of the hook-shapedends of the reinforcement fibers.

[0032] In a fourth embodiment, the length-diameter ratio of thereinforcement fiber bundle is at least 0.2 and maximally 5, morepreferably at least 0.5 and maximally 1.5. Expediently, thereinforcement fiber bundle is substantially cylindrical.

[0033] In a fifth embodiment, the length-diameter ratio of thereinforcement fibers is at least 40.

[0034] The reinforcement fibers may be made of steel with a tensilestrength between 500 and 3000 N/mm².

[0035] The present invention also relates, in another aspect thereof, toa reinforcement fiber bundle, comprising a number of substantiallyparallel reinforcement fibers for reinforcing a curable material, whichreinforcement fibers are joined at least at the ends thereof by means ofan adhering substance which loses its cohesion during the mixing of thereinforcement fiber bundles with at least the curable material, whereinthe ends of the reinforcement fibers are hook-shaped and that thereinforcement fiber bundle comprises end faces which are substantiallyevenly covered with the adhering substance. The advantage of the endfaces of the reinforcement fiber bundle being substantially evenlycovered with the adhering substance is not limited to any kind ofadhering substance, be it with or without secondary reinforcementfibers. Especially with hook-shaped ends there is a large risk ofentanglement of reinforcement fiber bundles, and hence of bridging insilos. By covering the end faces smoothly, the reinforcement fiberbundles are no longer able to become entangled in other fiber bundles.This also holds for separate reinforcement fibers already liberated inthe curable material. It is noted here that this latter effect forms amuch more severe problem with reinforcement fibers with hook-shaped endsthan with reinforcement fibers with straight ends.

[0036] Again, the limitations and advantages of the preferredembodiments of the reinforcement fiber bundle according to the firstaspect of the invention also hold for the reinforcement fiber bundle asmentioned in this third aspect of the invention.

[0037] In a first embodiment of the reinforcement fiber bundle accordingto the third aspect of the invention, substantially only the hook-shapedends of the reinforcement fibers are comprised in the adheringsubstance.

[0038] In a second embodiment the adhering substance is substantiallyinert with respect to the non-cured curable material.

[0039] Advantageously, the adhering substance is a curing substance.

[0040] Preferably, the adhering substance substantially comprises thecurable material.

[0041] More advantageously, the adhering substance substantiallycomprises mortar, concrete, gypsum, cement or a mixture thereof.

[0042] In a third embodiment, the adhering substance comprises secondaryreinforcement fibers.

[0043] Advantageously, the secondary reinforcement fibers comprise glassfibers and/or polypropene fibers with a diameter of maximally 100micrometer.

[0044] In a fourth embodiment, the length-diameter ratio of thereinforcement fiber bundle is at least 0.2 and maximally 5, morepreferably at least 0.5 and maximally 1.5. Even more preferably, thereinforcement fiber bundle is substantially cylindrical.

[0045] Advantageously, the length-diameter ratio of the reinforcementfibers is at least 40.

[0046] Preferably, the reinforcement fibers are made of steel with thetensile strength between 500 en 3000 N/mm².

[0047] With reference to the accompanying drawing, the invention will befurther explained into detail. In this drawing,

[0048]FIG. 1 represents a bundle of reinforcement fibers that are notjoined yet,

[0049]FIG. 2 shows a reinforcement fiber bundle according to theinvention,

[0050]FIG. 3 shows a detail of the reinforcement fiber bundle accordingto FIG. 2,

[0051]FIG. 4a-c show a schematic representation of the mixing ofreinforcement fiber bundles according to the invention with the curablematerial, and

[0052]FIG. 5. shows some examples of hook-shaped ends of fibers.

[0053] In FIG. 1, a reinforcement fiber bundle is generally indicated by1. The reinforcement fiber bundle 1 is made up of a large number ofparallel reinforcement fibers 2 with a hook-shaped end 3. Thereinforcement fibers 2 are kept together by means of a thread 4.

[0054] Although the reinforcement fibers 2 are represented withhook-shaped ends 3, they can in principle have any appropriate shapeaccording to the intended application.

[0055] The reinforcement fibers 2 can be made of any kind of materials,depending on the requirements made upon the fibers and upon the curablematerial that has to be reinforced and in which the fibers will be used.In the event of curable materials to be reinforced, we think of e.g.synthetic resins, concrete and the like. The material of which thereinforcement fibers are made can e.g. be glass, quartz, carbon orplastics. For concrete and concrete-like materials to be reinforced, itis recommended to preferably use metal reinforcement fibers. In mostcases, steel types with a high tensile strength, e.g. between 500 and3000 N/mm² are used.

[0056] The fibers may be straight, this is a cheap and simplerealization of reinforcement fibers. Preferably, the reinforcementfibers have a shape that renders it more difficult for the reinforcementfibers to slide out of the cured material under the influence of atensile load. Therefore, the fibers are e.g. corrugated or theircross-sectional surface varies over their length. In FIG. 1, thereinforcement fibers have hook-shaped ends. With such a shape, thefibers have to be deformed completely before they can be pulled out ofthe concrete or other material used.

[0057] The length-diameter ratio of the used reinforcement fibers is,because of practical and economic reasons, mostly comprised between 10and 200, and preferably at least 40. In the case of non-straight fibers,the length is the straight-lined distance between the ends of the fiber,whereas in the case of fibers of which the diameter varies over theentire length, the diameter is determined as the average diameter overthe entire length.

[0058] A reinforcement fiber bundle can consist of a variable number ofreinforcement fibers, e.g. between 10 and 2000, depending on the desiredshape of the reinforcement fiber bundle and the properties of thereinforcement fibers that are used. To keep the reinforcement fiberstogether until the adhering substance to be applied does so, thereinforcement fiber bundle can be equipped with temporary adheringmeans, such as an elastic, a thread etc., or the bundle is hugged by aclip, tongs, jaws or another mechanical device. Preferably, thetemporary adhering means that are used are so designed that they canstay in position around the bundle from the moment of bundling till theapplication and, if necessary, the curing of the adhering substance thatis to be applied later on. Afterwards, the temporary adhering means canbe removed. In certain cases, e.g. when a thread or elastic is used, thetemporary adhering means may stay in place. The mixing process is oftenso intensive that the adhering means are completely destructedmechanically. Preferably, these complementary adhering means are inertin relation to the curable material. It is e.g. possible to use a threadthat is made of the same material as the reinforcement fibers, in whichevent the diameter of the thread is smaller or in which thread a weakspot has been made, so as to allow the thread to break during the mixingprocess of the reinforcement fiber bundles with the curable material andto allow the reinforcement fibers to be liberated from the reinforcementfiber bundle.

[0059] Preferably, the additional adhering means are chosen in such away that the reinforcement fibers 2 of the reinforcement fiber bundle 1are kept together under tension. It is e.g. possible to use a tightelastic or a tight metal thread as additional adhering means. Aftermixing with the curable material and the crumbling of the adheringsubstance 5, the distribution of the reinforcement fibers 2 in thecurable material will be easier.

[0060] The shape of the reinforcement fiber bundle in FIG. 1substantially corresponds with a cylinder shape. The length-diameterratio of the reinforcement fiber bundle approximately is 1. In the eventof such shape, the reinforcement fiber bundles resemble “stones” or“coarse aggregate” and so only have a very small tendency to bridging inthe storage silos. By bridging, it is understood that the bundlesentwine in such a way in a storage silo that the pouring-out of the silois stopped: the bottom non-poured out fiber bundles then form a bridgereaching from one (side of the) wall of the storage silo to the other.Although a value of approximately 1 for the length-diameter ratio of thereinforcement fiber bundle is preferred, values comprised between 0.2and 5 can also be used.

[0061] The dimensions of the reinforcement fiber bundle are to a largedegree determined by the reinforcement fibers that are used. The lengthof these fibers mostly ranges between 0.25 and 10 cm though otherdimensions are also conceivable. The diameter of the cross-section of areinforcement fiber bundle preferably ranges between 0.25 and 10 cmwhereas other values are also possible.

[0062]FIG. 2 shows a reinforcement fiber bundle 1 in which the ends 3 ofthe reinforcement fibers 2 are joined in each case by applying a layerof adhering substance 5.

[0063]FIG. 3 gives a detail of FIG. 2 in which the ends 3 of thereinforcement fibers 2 are covered with an adhering substance 5. In theadhering substance 5, there are integrated very fine polypropenesecondary reinforcement fibers 6. The layer thickness of the adheringsubstance 5 is approximately as large as the length of the hook-shapedend 3.

[0064] It is possible to cover the sides instead of the ends 3, butcovering the ends is preferred as it is in that way possible toefficiently avoid that the mostly hook-shaped ends 3 of thereinforcement fibers 2 of different reinforcement fiber bundles 1entangle, and thus that bridging occurs in a storage silo forreinforcement fiber bundles.

[0065] The adhering substance 5 is inert in relation to the curablematerial to avoid that the properties of the material are negativelyinfluenced. Preferably, the material of the adhering substance issubstantially equal to the curable material, e.g. concrete. As a result,it is ensured that the properties of the final reinforced cured materialare not or practically not influenced. Other adhering substances, suchas several ceramic masses, are also possible.

[0066] Possible brittleness of the adhering substance 5 or itsresistance to breaking under (mechanical) loads can amongst others beset by choosing the appropriate ratio of binding agent, sand and thelike. Sometimes, the strength to be obtained is insufficient to ensuregood transport properties, a good manageability, etc. In such event, theadhering substance can in turn be mixed with secondary reinforcementfibers 6. It is e.g. possible to embed polypropene or glass fibers, witha diameter between 0 and 100 μm, in the adhering substance. By addingsuch fibers, the adhering substance's tensile strength and the generalresistance against breaking under mechanical load increase. So, thereinforcement fiber bundles 1 remain intact during transport, storage,etc., without having to take special measures. The secondaryreinforcement fibers 6 can contribute to the improvement of theproperties of the curable material.

[0067] The adherence substance 5 is applied to both sides of the fibers2 in the reinforcement fiber bundle 1 of FIGS. 2 and 3. It is alsopossible that the entire reinforcement fiber bundle 1 is surrounded oreven impregnated by the adhering substance 5 or that only one end of thefiber bundle 1 is covered with the adhering substance 5. But it has tobe said that this is not to be preferred. You either have to use anexcessive quantity of adhering substance, as a result of which thestrength of the reinforcement fiber bundle 1 increases in such a waythat the time during which it has to fall apart during the mixingprocess with the curable material excessively increases, or the ends 3at one side of the reinforcement fibers 2 stay free, as a result ofwhich the ends of the reinforcement fibers of the reinforcement fiberbundles 1 can entangle and so cause bridging of the reinforcement fiberbundles 1.

[0068] The adhering substance 5 can be applied by means of smearing,spraying, brushing, dipping the desired quantity, etc. In addition, thereinforcement fiber bundle 1 can be immersed or pushed in a holder withadhering substance 5 to the desired impregnation depth. Once theadhering substance is applied, it can be cured, if so desired, by dryingit in the air, a heat treatment, a combination of both or in any otherappropriate way.

[0069]FIGS. 4a-c represent a method for mixing reinforcement fiberbundles according to the invention with curable material in a holder.

[0070] In FIG. 4a the reinforcement fiber bundles 1 are situated in astorage holder 7 with at the bottom side a lockable mouth 8 that can beopened by means of a moveable slide 9. Under the mouth 8, there is aholder 10 that contains the curable material 11. The slide 9 is openedand the reinforcement fiber bundles 1 pour out of the storage holder 7in the curable material 11.

[0071] The reinforcement fiber bundles 1 are not always directly addedto the curable material 11, as shown in FIG. 4a. It is also possible tofirst store the components of the curable material in separate storagesilos and to have the exact quantities of the components flow in theholder 10. It is also possible to move the reinforcement fiber bundles 1from the storage silos via a conveyer belt to holder 10. In such event,it is recommended to avoid bridging of the reinforcement fiber bundles 1in the storage silo concerned.

[0072] In FIG. 4b the reinforcement fiber bundles 1 are already somewhatdistributed amongst the curable material 11 with the help of the mixingmeans (not represented). This figure also shows decreased fiber bundles12 and loose reinforcement fibers 2. Rests of adhering substance 13stick to some loose reinforcement fibers 2, as loose rests of adheringsubstance 13 are also spread in the curable material.

[0073] In FIG. 4c all reinforcement fibers 2 are separated, while restsof adhering substance 13 are spread through the entire curable material.After curing of the curable material 11 these rests only form granulesthat are incorporated in the material, while, if the adhering substance5 and the curable material 11 substantially correspond, there onlyremains a homogeneous material with reinforcement fibers after curing ofthe curable material, in which homogeneous material there can not befound any rests of adhering substance.

[0074]FIG. 5 shows some examples of reinforcement fibers withhook-shaped ends. As mentioned above, this includes deformed ends. Inthe Figure, there are shown from left to right:

[0075] a first hook-shaped end,

[0076] a second hook-shaped end,

[0077] a flattenend end,

[0078] a tortuous end, and

[0079] a head-like end.

[0080] Such ends offer superior properties as to increased tensilestrength of the cured curable material. It is possible for the fibers tohave one or two hook-shaped ends.

EXAMPLE

[0081] Experiments have been carried out, using the following adheringsubstance. a) cement 86.52% by weight b) polyvinyl alcohol 4.02% byweight c) water 9.38% by weight d) polypropene fibers 0.08% by weight

[0082] This adhering substance resulted in excellent properties of thefiber bundles. In general, they did not break during transport, whenexperiencing shocks, or even when falling. Yet, during mixing with thecurable material, the individual fibers were released efficiently andreliably.

1. Reinforcement fiber bundle (1), comprising a number of substantiallyparallel reinforcement fibers (2) for reinforcing a curable material(11), which reinforcement fibers (2) are joined at least at the ends (3)thereof by means of an adhering substance (5) which loses its cohesionunder the influence of mechanical forces during mixing of thereinforcement fiber bundles (1) with at least the curable material (11),wherein the adhering substance substantially comprises a material whichis substantially inert with respect to the non-cured curable material(11), the adhering substance (5) substantially comprising the curablematerial (11), characterized in that the adhering substancesubstantially comprises mortar, concrete, gypsum, cement or a mixturethereof.
 2. Reinforcement fiber bundle (1) according to claim 1,characterized in that the adhering substance (5) comprises secondaryreinforcement fibers (6).
 3. Reinforcement fiber bundle (1) according toclaim 2, characterized in that the secondary reinforcement fibers (6)comprise glass fibers and/or polypropene fibers with a diameter ofmaximally 100 micrometer.
 4. Reinforcement fiber bundle (1) according toone or more of the preceding claims, characterized in that thelength-diameter ratio of the reinforcement fiber bundle (1) is at least0.2 and maximally
 5. 5. Reinforcement fiber bundle (1) according to oneor more of the preceding claims, characterized in that thelength-diameter ratio of the reinforcement fiber bundle (1) is at least0.5 and maximally 1.5.
 6. Reinforcement fiber bundle (1) according toone or more of the preceding claims, characterized in that thereinforcement fiber bundle (1) is substantially cylindrical. 7.Reinforcement fiber bundle (1) according to one or more of the precedingclaims, characterized in that the length-diameter ratio of thereinforcement fibers (2) is at least
 40. 8. Reinforcement fiber bundle(1) according to one or more of the preceding claims, characterized inthat the reinforcement fibers (2) are made of steel with a tensilestrength between 500 and 3000 N/mm².
 9. Reinforcement fiber bundle (1)according to one or more of the preceding claims, characterized in thatthe ends (3) of the reinforcement fibers (2) are hook-shaped. 10.Reinforcement fiber bundle (1) according to one or more of the precedingclaims, characterized in that the bundle comprises end faces, which aresubstantially evenly covered with the adhering substance (5). 11.Reinforcement fiber bundle (1) according to claim 9 or 10, characterizedin that substantially only the hook-shaped ends (3) of the reinforcementfibers (2) are comprised in the adhering substance (5).
 12. Method forjoining reinforcement fibers (2) to reinforcement fiber bundles (1) forreinforcing a curable material (11), in which reinforcement fibers (2)are bundled in a substantially parallel position and at least at theirends (3) are joined, wherein the reinforcement fibers (2) are joined byapplying an adhering substance (5) to at least the ends of thereinforcement fiber bundle (1), which adhering substance issubstantially inert in relation to the non-cured curable material (11)and which substance loses its cohesion under the influence of mechanicalforces during the mixing process of the reinforcement fiber bundles (1)with at least the curable material (11), characterized in that theadhering substance (5) substantially comprises the curable material(11), and substantially comprises mortar, concrete, gypsum, cement or amixture thereof.
 13. Method according to claim 12, characterized in thata curing adhering substance (5) is applied and then cured.
 14. Methodaccording to claim 12 or 13, characterized in that the substantiallyparallel bundling of the reinforcement fibers (2) takes place undertension.
 15. Reinforcement fiber bundle (1), comprising a number ofsubstantially parallel reinforcement fibers (2) for reinforcing acurable material (11), which reinforcement fibers (2) are joined atleast at the ends (3) thereof by means of an adhering substance (5)which loses its cohesion during the mixing of the reinforcement fiberbundles (1) with at least the curable material (11), characterized inthat the adhering substance (5) comprises secondary reinforcement fibers(6).
 16. Reinforcement fiber bundle (1) according to claim 15,characterized in that the secondary reinforcement fibers (6) compriseglass fibers and/or polypropene fibers with a diameter of maximally 100micrometer.
 17. Reinforcement fiber bundle (1) according to claim 15 or16, characterized in that it comprises end faces which are substantiallyevenly covered with the adhering substance (5).
 18. Reinforcement fiberbundle (1) according to one of claims 15-17, characterized in that theends (3) of the reinforcement fibers (2) are hook-shaped. 19.Reinforcement fiber bundle (1) according to claim 18, characterized inthat substantially only the hook-shaped ends (3) of the reinforcementfibers (2) are comprised in the adhering substance (5). 20.Reinforcement fiber bundle (1), comprising a number of substantiallyparallel reinforcement fibers (2) for reinforcing a curable material(11), which reinforcement fibers (2) are joined at least at the ends (3)thereof by means of an adhering substance (5) which loses its cohesionduring the mixing of the reinforcement fiber bundles (1) with at leastthe curable material (11), wherein the ends (3) of the reinforcementfibers (2) are hook-shaped and that the reinforcement fiber bundle (1)comprises end faces which are substantially evenly covered with theadhering substance (5), characterized in that substantially only thehook-shaped ends (3) of the reinforcement fibers (2) are comprised inthe adhering substance (5).